(1) A control network used in process control and industrial automation. Fieldbuses are bi-directional, digital serial networks that offer services at layers 1 and 2 of the OSI model (physical and data link). Some fieldbuses offer services at layer 7 as well. Examples of fieldbus networks are FOUNDATION fieldbus, DeviceNet, ControlNet, Modbus and PROFIBUS. In the 1980s, fieldbuses began to replace the parallel wiring used in 4-20 mA and +/-10 volt analog interfaces.

(2) (FOUNDATION fieldbus) A control network typically used in the process control industries from the Fieldbus Foundation (FF). Using a distributed architecture where the control is in the devices themselves, FOUNDATION fieldbus integrates low-speed sensors and actuators with high-speed controllers and servers in a single system. FOUNDATION fieldbus is made up of two networks: lower-speed H1 and high-speed HSE.

H1 is a bus-powered, serial, multi-drop topology at 31.25 Kbps that replaces 4-20 mA circuits, but can communicate with 4-20 mA devices via converters. Introduced in 1995, H1 provides services at layers 1, 2 and 7 of the OSI model.

HSE (High Speed Ethernet) provides 100 Mbps between PLCs, servers and workstations. It also connects to H1 networks via the linking device that multiplexes H1 segments together. Introduced in 2000, HSE provides services at layers 1, 2, 3, 4 (Ethernet and TCP/IP) and layer 7 of the OSI model. For more information, visit www.fieldbus.org.